You can sue a restaurant for finding an ant on the food. However, if you suffer food poisoning or fall ill due to the insect in your food, then you can be able to sue them. Bear in mind that you have to show that your sickness was caused by the insect in your food.
I know if it was me id be making a call from jail because I would tear the place to shreds if I found ANYTHING crawling in my food! This is AMERICA not some foreign country! oops accidentally on purpose hit the gas instead of the brake and ran through the front window bat sheet crazy if they did that to me! I have anger issues what can I say? Ever see the movie with Michael Douglas called "Falling Down" or how about any of the Tyler Perry movies that feature Madea? Even though she isn't real I can tell we have alot in common. There are certain things you just don't do. Yes I know it happens, I watch Gordon Ramsey, I'm not that naive but I best not SEE it happen!
No to to sue anyone.. That's severely drastic, unless u got some kinda weird or non heard of illness due to this. My reaction would be make a complaint to manager, corporate or ever ur states public health department to file a complaint. And u don't ever need to eat there again but with good ethics and effort u can help someone else from finding ants in their food